The invention is based on an armature packet for an electric motor.
For producing armature packets for electric motors, individual armature laminations are stamped in such a way that recesses for armature windings are stamped into the lamination in the same operation. The armature windings are wound into these winding slots and fixed in their position by impregnation with a suitable material. In principle, there are two known methods for this.
In dip roller-burnishing, the wound armature packet is sealed by being dipped and rolled in the impregnating material (such as polyester resin). Next, the impregnating material is hardened, so that the winding together with the armature packet forms a rigid structure. In the drip process, a variant of dip roller-burnishing, the armature packet is received, rotating, in a suitable device and the impregnating material is dripped onto it. Next, the impregnating material is hardened as in dip roller-burnishing. However, in dip roller-burnishing and the drip process, the problem is that the impregnating material does not always penetrate all the voids between the armature windings. To assure that these voids will be completely filled, all the process parameters, such as temperature, viscosity, winding density of the wires, and venting, must be optimally adapted to one another and adhered to as exactly as possible. Otherwise, uneven filling of the winding slots with impregnating material and air inclusions, which thus leads to the formation of bubbles. As a result, the windings are fixed only inadequately in their position against the centrifugal forces that occur in operation and against vibration. As a consequence, short-circuited coils occur along with vibration from radial shifting of the armature winding and hence of the center of mass, resulting in a shorter service life of the motor.
In armoring, for additional fixation, so-called cross bandages of paper or plastic cords are used. These bandages on the one hand provide a certain protection of the windings from abrasive grinding powders and on the other provide an additional positional fixation of the windings in the packet. As a result, while the defects of impregnation are essentially compensated for, nevertheless this method is very complicated and thus expensive in the production process, and so it is employed only for high-quality motors.